Cellular activities occurring during the course if in vitro palate closure are being studied using a circulating, submerged organ culture system. Results of studies of uptake of 3H-thymidine, -uridine and -leucine are being analyzed. Further studies monitoring the uptake of 35S-sulfate and 3H-proline will be conducted. Correlations of cell activities with the degree of palate closure will be made. Following analyses of these data and identification of peak periods of cellular activity, specific inhibitory substances will be employed to determine if these activities play a role in palate closure.